When you design a new engine, you get the available options, as the basic layout.
(f.ex. in 1910, you can only make up to V6's.)
However, you can make V10, V12 etc. if you select it, after you've chosen the basic layout.
See screenshot.
I just realized ive posted a similar bug later than this one mentioned, that is actually the same bug. It seems my search before posting it missed it and the title of the thread is a bit ambiguous which contributed as well i think.
(rather than making engines you cant, i think the bug is probably more specific, having a number of cylinders you cant normally at your skill level. I would and did title it something like "Design Engine Screen allows all Cylinder numbers")
Seeing as this thread is the oldest, ill copy my post into it and delete the one i posted later. (just following the bugs forum rules that ask you not to duplicate bug threads.)
Thread Copy pasted below:
When you go to R&D-Design-Engine, it limits the number of cylinders according to your skill as normal.
However once your in the actual design screen where you adjust sliders, you seem to be able to change the number of cylinders at will.
An example:
I chose to design a V6 engine in 1910/11, the maximum number of cylinders i could make it with was 6 in the R&D-Design-Engine button.
Once i entered the Design mode(where you adjust sliders), i could freely select anything from 2-16 cylinders.
Ive attached screenshots as well to make it clear what im talking about.
Bug has been fixed for 1.12!